Developer process and apparatus



April 25, 1961 J. HRUBY ETAL DEVELOPER PROCESS AND APPARATUS 5 Sheets-Sheet 1 Filed March 6, 1958 INVENTOR. 70.5525 A zaey P404 3, 5725/09 52 Ja 4. 7256/9) flrrae/nsr April 1961 J. HRUBY ETAL 2,981,171

DEVELOPER PROCESS AND APPARATUS Filed March 6, 1958 3 Sheets-Sheet 2 l T I I 5, 33 2d 28 Z; 34 39 l 35 m i :r: I

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INVENTOR.

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FIG. 3 Jaw/V A. fink-614V @Wmwu April 25, 1961 J. HRUBY ETAL 2,981,171

DEVELOPER PROCESS AND APPARATUS Filed March 6, 1958 I5 Sheets-Sheet 3 United States Patent ice 2,981,171 DEVELOPER PROCESS AND APPARATUS Joseph Hruby, Deerfield, Paul B. Streich, Sr., Fox Lake, and John L. Tregay, Broadview, Ill., assignors to Charles Bruning Company, Inc., Mount Prospect, 11]., a corporation of Delaware Filed Mar. 6, 1958, Ser. No. 719,619

9 Claims. (Cl. 95-94) This invention relates to processes and apparatus for the application of developer solution to photoprints and more particularly to the so-called semi-wet process and apparatus for applying developer solution to diazo type reproductions. This application is a continuation-in-part of our copending application Serial No. 574,739, filed March 29, 1956, and now abandoned.

Developer processes and apparatus heretofore known have involved a trough for the developer solution and a smooth surface or grooved roller, including a capillary grooved roller, partially submerged in the solution in the trough. The prints are passed in direct contact with the partially submerged roller and the solution is thus.

applied thereto. Such developers have been proposed in which only one partially submerged roller is used, in which case the solution is applied to one side only of the prints, or in which two partially submerged rollers are used and the prints passed between the two rollers, in which case the solution is applied to both sides of the prints.

Developer apparatus heretofore known is objectionable for a number of reasons, some of the more important of which are:

(1) Smooth roller developers do not apply the solution uniformly throughout the entire area of the prints. By a starter is meant that the leading end of the prints in the direction of movement through the developer has less solution applied thereto than the remainder of the prints, the amount gradually increasing in the direction of movement until it reaches a maximum value equal to that applied to the rest of the prints. This objection is particularly acute in connection with the treatment of small prints, say, forexample, letter size prints. In the treatment of such small prints by heretofore known procedures they are frequently underdeveloped at their leading ends and oversaturated at their trailing edges. It is not unusual for the leading A of an inch or thereabout portion of the prints to be completely dry, or almost dry, as compared with the remainder of the prints. This results in a swelling or expansion of the prints except at the leading ends, with subsequent distortion of the prints producing a wave-like contour rather than a flat sur face. Often the final result, after the prints pass through the dryer, is a puckered or rippled surface.- Attempts made to iron such prints have not been successful.

(2) In the case of the capillary roller type of developer, when operating at speeds of about 12 to 15 feet per minute or faster, for all practical purposes the capillaries are functionless. Rather than resulting in the application of the metered amount of solution as intended to the prints, the result at such speed is the application of 2,981,171 Patented Apr. 25, 1961 an excess over the desired amount. This excess increases with an increase in speed of the prints. This entails the use of a greater amount of heat for etfecting'the drying and requires the use of larger drying chambers than would otherwise be necessary. Furthermore, the more moisture applied and removed, the greater the loss of the original smooth surface of the prints.

(3) In general, the speed of the prints through the heretofore used developer apparatus for diazo type reproductions has had a considerable influence on the amount of developer solution applied to the prints. Such apparatus is usually equipped with variable speed drives, synchronizing printing and developing sections, to enable the operator to control the speed of prints therethrough. As a consequence, prints requiring different speed settings have received different amounts of developer solution. Thus, if the concentration of chemicals in the developer solution is adjusted to provide the correct amount for a print developed at a slow machine speed, an excess is necessarily applied at the higher speeds with consequent waste of developer solution and formation of poor prints because a large excess of developer solids deleteriously affects the quality of the finished prints. The reverse is also true, if the concentration of developer solids is correct for higher speeds, as deficiency is applied at the lower speeds.

(4) An ideal amount of solution would be just enough to have good coupling of the diazo dye and just enough to spread uniformly over the entire area of the prints. With such minimum amount of developer solution there is practically no marked swelling or expansion of the paper fibers and smooth prints requiring a minimum of.

It is another object of this invention to provide a developer process and apparatus which result in a substantially uniform application of the developer solution to the prints and this irrespective of the speed of the prints through the developer, including speeds as high as 60 to feet per minute and even higher.

It is still another object of this invention to provide a developer process and apparatus in which the developer solution left on the print is substantially less than heretofore, with consequent decrease in the amount of liquid requiring evaporation in the drying of the prints.

Other objects and advantages of this invention will be apparent from the following detailed description thereof.

In accordance with this invention, the prints are passed through a pool of developer solution, desirably formed as a meniscus by a pair of rotating wringer rollers, this pool being maintained by the rollers in amount greater than that which the print can absorb in the time required for it to pass therethrough so that the prints have ap plied thereto in their passage through the pool an amount of developer solution greatly in excess over that required for the development of the prints, and thereafter stream the prints are passed through the. wringer rollers where they are subjected to pressure and the excess solution is removed leaving in and on the prints uniformly distributed the correct desired amount of the developer solution. The amount of the excess solution thus applied is not critical. It may be from one to ten times by weight over and above the amount required for development of the prints to give excellent prints. Excesses above ten times the amount required to give excellent prints, as a practical matter, should be avoided to elirninate the necessity of designing the apparatus to' handle such a large excess of solution.v

The minimum amount of developer solution applied to the print should bethat amount which issuflijcient to supply the stoichiometric amount of; coupling ee'mg ponent to react with thefdiazo salt onthesheet; inpractice it has been found beneficialto use an excess o'flcoupling component above this minimun'ramount' to insure.

complete and'r apid-development'.

It will be apprecia ed; that, irrespectiveof the amount of excess taken' up. by the prints in their passage through the pool of developer solution, such excess is pressed.

from the prints by the wringer or squeegee rollers. They control the amount'of developer solution left in and on the print: uniformly distributed therethroughout. These rollerscan readily'be adjusted to exercise the, necessary pressure on the wetprints to leave thedesired amount of developer solution in and'on' the prints, irrespective of the speed of movement of the prints. therethrough, within practical limits. The expression wringer roller? will be used hereinafter andin the claims torefento:

these rollers. Itwill be understoodthat these; rollers exercise a squeegee action to press out or olf the print the excess solution, andthe expression wringer is used in this sense.

In accordance with a preferred embodiment of the present. invention, the prints are first passed through a pool of developer solution formed'as a meniscus by a pair of rotating applicator rollers.

developer solution is appliedthereto. The Wet prints are then passed througha soaking zone where the devel-.

oper solutiorris afforded the opportunity of soaking into the prints. Thissoaking zone. is-positioned between the applicator rollers and a. pair of wringer rollers In-the; passage of the wet prints through-the wringer rollers which, as noted are suitably spaced relative to the applicatorrollers, the. excess; solution ispressed fromthe prints Thus, the print s-leavingtthe wringer rollers have the desired amount of; developer solution applied thereto requiredifor development of the; printsto give optimum results.

In the accompanyingdrawings --forming a part of this specification and showing; for purposes of exemplification, preferred forms of this invention without limiting the claimed invention to such illustrative instances:

Figure 1 isa fragmentary vertical section, partially in Figure 6 is adiagrammatic vertical section showing a In the passage of. the prints through this pool of solution, an excess of modified arrangement of feed and wringer rollers and illustrates the formation-of a pool of developer solution at the bite between the wringer rollers which results in the application of a greater amount of developer solution to the face or side of the print to be developed than that applied to the back or opposite side of the print;

Figure 7 is a diagrammatic vertical section showing still another modification embodying this invention, in which modification a roller is employed to apply developer solution to the face of the print prior to passage through the wringer rollers to allow more time for the developer solution to soak into the face of the print before the excess is removed by the wringer rollers;

Figure 8 is a diagrammatic vertical section showing still another modification embodying this invention, in which modification, a pair of applicator rollers is, employed to apply developer solution to the prints prior to their passage through the wringer rollers. toprovide a suitable time interval in the passageof the prints between these two sets of rollers, for, the developer. solution to soak into the prints before wringing excess solution therefrom; and

Figure 9 is a fragmentary enlarged sectional view through the pair of applicator rollers showing the surface construction of these rollers.

Referring first to Figures 1 to 4, inclusive, the exposed print leaves the printing unit on a conveyor band 11 (Fig. 1) driven by roller 12 mounted for rotation on frame 13 of the machine. A cooperating print feed roller 14 is mounted contiguous to the discharge end of the feeding tape orband 11. Since the printing unit may be of anyknown type and per se is not'partofQthisinvention, it is believed further description thereof is unnecessary. 7

Guides 15 and 16 are positioned on frame 13 to guide the prints between the troughs 17 and 18 suitably fixed to frame 13. The sides-17' and 18 of troughs 17 and 13 form a guide throat for the prints, the direction of movement of which through the machine is indicated by the arrows of Fig. l. Removably mounted in troughs 17 and 18 are a pair of grooved rotatable feed rollers 19 and,21, respectively. These rollers are partially submerged in the developer solution 22 contained in troughs, 17 and 18. The shafts 23 and 24 (Fig. 2) of rollers 19' and 21, respectively, are journalled for rotation in bearings 25 on yoke 26, pivoted at 27 and 28 to the frame 13. These shafts are provided with meshing gears 29 and 31, desirably synchronously driven from the drive (not shown) for the printing unit.

Yoke 26 is suitably braced by front crosspie has securedthereto as at 33. and; 34a bearingretainingplate'35, and at ,36 and ,37 an oppositely disposed bear-- ingretainingi plate 38. Wringer rollers 39 and .1 aremounted on the yoke 26 so that theyrest on the feed rollers 19 and 21, respectively, as shown in Figs. 1 and 3. For this purpose bearing retaining plates 35 and 38 are each provided with a U-shaped bearing slot 42 (Fig. 3) in which the shaft ends 39' of roller 39 are disposed.

Contiguous to the upper edge of bearing slot 42in each of the bearing retaining plates 35 and 38' is angular track 43. Shafts 44 of weighted roller 45 ride on these angular tracks 43 on thebearing plates 35 and 38. In this way, wringer roller 39 rests on feed roller 19 under its own weight and the weight exerted suit by roller 45.

The other wringer roller 41 is disposedbetween the bearing retaining plates 35 and 38 resting on feed roller 39, as'shown in Figs.- 1 to 3, inclusive. The bearing-re tainingplatesSS and 38 are each'provided with an angle slot 46.- The shaft-ends 47 of weighted roller 48 aremounted' in the angle slot 46. Thus wringer roller 41 rests on feedrolle'r 21 not only under its own weight but HISOllIldCl' the weight exerted by roller 48. The weighted rollers 45 and 48 desirably are steel rollers. They serve to maintain the wringer rollers 39 and 41 in tangential contact'with-each other under a predetermined pressure letter size, more or less, may have the shafts of the wringer rollers mounted in bearings which are spring pressed toward each other. The pressure exerted by the wring r rollers on the prints passing therethrough can readily be controlled by adjusting the spring pressure.

In the structure of Figs. 1-3 the wringer rollers 39 and 41 are driven by frictional contact withqthe feed rollers 19 and 21. If desired, the shafts for the wringer rollers may be provided with suitable gears driven synchronously with the drive for the feed rollers or that of the printing machine.

The apparatus of Figs. 1-3 permits the ready removal of the feed rollers 19 and 21 from the developer solution 22 in troughs 17 and 18 whenever it is desired so to do for cleaning or for other purposes. This is readily'accomplished by moving the yoke 26 about its pivotal supports 27 and 28, thus bodily lifting the feed rollers 19 and 21 from the troughs in which they are disposed. This movement of the yoke effects movement of the entire assembly of the feed rollers 19, 21, the wringer rollers 39, 41, and the weighted rollers 45, 48, all of which are carried by the yoke 26 as hereinabove described.

Pivoted to frame 13 as at 51 is a support 52. Two such supports are provided one on each side of the machine, and they are connected by a crosspiece 53 which carries spaced guide fingers 54 extending downwardly toward the wringer roller 41. These fingers 54 guide the prints as they leave wringer rollers 39 and 41 so that theprints pass over a guide roller 55 desirably mounted on support 52. From the guide roller 55 the prints move to a conveyor belt or tape 56 which passes over a driven roller 57 suitably mounted for'rotation in the frame 13. Belt 56 carries the prints having the developer solution uniformly distributed thereon to and through the dryer (not shown) which may be of any conventional type.

As best shown in Fig. 4, each feed roller which may be of suitable material such as steel, is provided with grooves 58 at spaced intervals along its length. These grooves may be about $6 of an inch deep, of various pitch, if spiral grooves are used, and may be widely spaced apart although it is preferred to have them with relatively small land, i.e., narrowly spaced. Thus, for example, the grooves may be 0.062 inch wide and spaced apartapproximately 0.250 inch. The grooves permit a certain amount of solution to pass through them at the zone of contact solution maintained in each trough. These layers are indicated by reference characters 61 and 62; the showing in the drawings is exaggerated somewhat for the sake of clarity of illustration. The solution thus brought up into the bite between wringer roller 41 and feed roller 21 is in part returned through grooves 58 in roller 21 to the body of solution 22, and in part transferred to the surface of roller 41. The grooves 58, as above explained, permit an excess of solution to pass through the zone of contact between the feed roller 21 and wringer roller 41; this excess is picked up by the rotating periphery of roller 41. A similar action takes place between feed roller 19 and wringer roller 39. Rollers 39 and 41 thus produce the meniscus or pool 59 which provides an amount of developer solution in excess of that which the print 63 can absorb or have deposited on its surface in its passage through this pool of liquid, irrespective of the speed of movement of the print This speed may be as low as through the pool 59. six inches per minute and as high as seventy feet per minute or even higher.

The pool or meniscus 59 is maintained at the underside of the wringer rollers 39 and 41 at any speed of practical operationwithout dripping, and this whether or not the prints pass therethrough. This is due to surface tension between the developer solution and the surface of the wringer rollers. The pool or meniscus 59 builds up to an equilibrium point and thereafter draining takes place toward the feed rollers and ultimately to troughs 17 and 18. The equilibrium point is controlled by the size of the grooves in the feed rollers 19 and 21. The use of grooves of the dimensions above noted, results in a pool containing an amount of solution greatly in excess of the required amount, and even in excess of that which the print is capable of taking up in its passage through the pool.

The print from the pool 59 passes through the. bite between the wringer rollers 39 and 41 where the excess solution is pressed therefrom, and returned to the pool 59. The prints leaving the wringer rollers 39 and 41 have the desired uniform amount of developer solution applied thereto. For most prints, approximately four grams per square meter of print is satisfactory. With this invention, once the pressure of the wringer rollers is properly adjusted, prints leaving these rollers invariably have the correct amount of developer solution uniformly applied thereto and this, irrespective of the speed of movement within all practical limits.

between the feed rollers and the wringer rollers, thus insuring a surplus of solution passing through the zone of contact between the feed and the wringer rollers to produce a pool of liquid 59 at the bite between the wringer rollers.-

The wringer rollers 39 and 41 desirably consist of a core of metal on which is superimposed a resilient, smooth surface of soft rubber or other resilient plastic material such as polyethylene, polyvinyl chloride or the foam plastics in which the surface is constituted of closed cells. These wringer rollers may exert a force of from about one to six pounds, preferably from two to four pounds per lineal foot, on the prints passing therethrough.

In operation, as diagrammatically illustrated in Fig. 5, rotation of the feed rollers 19 and 21 in troughs 17 and 18 inthe directions indicatedby the arrows on these rollers, causes a layer of solution to be carried on the surface of I the feed rollers from body 2205 In the modifications of Figs. 6 and 7, the feed rollers, wringer rollers and weighted rollers are identified by' the same reference characters as the corresponding rollers of Figs. 1 and 5.

Referring to Fig. 6, feed rollers 19 and 21 are mounted.

for rotation in the troughs 65 and 66, respectively. A

trough 65. This guide 67 cooperates with the throat guide 69 formed by side walls 68 and 71 to guide the prints in their movement into the bite between the wringer rollers 39, 41. The throat guide 69, it will be noted, is disposed laterally to one side of the bite between wringer rollers 39, 41. of movement of the prints through the wringer rollers is substantially as shown in Fig. 6; it will be noted prints are deflected when they leave the guide throat 69 and enter the bite between the wringer rollers 39 and 41. This increases the meniscus or pool of developer solution contiguous to wringer roller 41, as indicated at 72. Since the prints are fed with their faces, i.e., the sides to be developed, in contact with the periphery of roller 41, the contact of the face of the sheet with the larger meniscus or pool at 72 results in application of more developer solution to the face of the prints than to their backs. This modification, as is clearly evident from Fig. 6, allows slightly more time for soaking of the developer solution into the face of the In this way, the path 6' print, where the developerv solution is needed, because the face of each print comes into contact with the developer solution at 72 before the back of the. print passes through the solution at 73.

The modification of Fig. 7' shows still anotherembodiment of' the invention in which more developer solution is applied to the face than to the back of each print, and additional time, as compared with the mode of operation involvedin the embodiment of the'invention shown in Fig. is provided for the! developer solution to penetrate and soak into the face of each print. Feed roller 19 is mounted for rotationin trough 73 and feed roller 21 in a second trough 74"provided with a lateral extension 75. A smaller feed roller 76 is mounted for rotation directly above extension 75. The periphery of feed roller 76 may be of metal or rigid plastic and may be grooved as hereinabove described in connection with feed rollers 19 and 21. Roller 76 is placed so that its periphery is close to but not in contact with the periphery of roller 21 producing a continuous layer 77 of developer solution on the roller 76, all or a portion of which solution is transferred to the face of the prints as they pass over roller 76 from the guide throat 78 formed by a suitably mounted guide 79 and a side wall of trough 73. From the feed 'roller 76 the prints pass through the meniscus 80 formed between Wringer rollers 39 and 41, the prints following the somewhat curved path indicated to allow ample time for penetration and soaking of the solution applied by roller 76 into the face of the print.

In the modification of Fig.' 8 the feed rollers are identified by the same reference characters as the corresponding rollers in Figs. 5, 6 and 7. They are mounted for rotation in the troughs 81 and 82. A pair of applicator rollers 83 and 84 are mounted with the periphery of roller 83 in surface contact with feed roller 21 and the periphery of roller 84 in surface contact with feed roller 19 and the two applicator rollers in tangential and feeding contact with each other, as shown in Fig. 8. Both of these applicator rollers 83 and 84 desirably are grooved as at 85 (Fig. 9) to facilitate flowback of solution. For example, a V-shaped helical groove or thread, 0.01 inch deep, 0.01 inch wide and having a /s inch pitch, is satisfactory. Any groove not wider than approximately inch and which does not become easily clogged can be used.

Wringer rollers 86 and 87, either or both of which may be of soft rubber or other resilient plastic material, as shown in Fig. 8, are disposed spaced from applicator' rollers 83 and 84 with roller 86 in surface contact and hence in driving engagement with feed roller 21. If only one of. the Wringer rollers 86 or 87 is made of rubber or soft plastic, to obtain the best wringing action a softer rubber or other plastic is preferably used for that roller than would be used if both rollers were of soft rubber or other plastic. A back-up or weight applying roller 88 exerts weight on Wringer roller 87 to have it cooperate with Wringer roller 86 to exert the desired wringing pressure on prints passing therethrough.

In the operation of the modification of Fig. 8, it is unimportant in which direction the print faces. Substantially the same amount of developer solution is applied to both the face and back of each print. Feed rollers 19 and 21 in their rotation apply developer solution to grooved applicator rollers 83 and 84 which are rotated by the rotating feed rollers 19 and 21. A pool or meniscus '39 of developer solution thus forms at the bite between applicator rollers 83 and 84. This pool builds up to an equilibrium point and thereafter drainage takes place toward the feed rollers 19 and 21 and ultimately to troughs 81 and 82, respectively. The equilibrim point is controlled by the size of the groovesin the peripheries of the applicator rollers 83 and 84 and in the peripheries of the feed rollers 19 and 21. The use of feed rollers and applicator rollers having grooves, as above' disclosed, results in a pool contain ing an amount of solution in excess of'the' required amount.

In the passage of the wet prints through the space 5 91 between the, applicator rollers 83, 84 and Wringer rollers 86 and 87 soaking of the developer solution into theprints takes place before the excessis' wrung therefrom; The wringing; of the. excess takes place as the prints passthrough and leave the Wringer rollers 86 and 87'. By havingwring'er' roller" 86in surface contact with feed roller 21, not onlyis it driven by the feed roller 21 but it ismaintai'ned wetalways, thus insuringproper functioning of the Wringer rollers. The excess solution removed from the printsby the Wringer rollers forms the pool 92 at the bite between the Wringer rollers 86 and 87. Where a large excess is applied to the prints, the excess developer solution wrung from the prints will initially form the pool 92 and will drain there from along the periphery of-the Wringer roller 86 and ultirnate- '20 1y reach the periphery of feedroller 21 which supplies it to the applicator roller 83; developer solution left on feed roller 21 after it leaves applicator roller 83 is fed to the t'rough81i It will be understood that in all modifications the developer solution in the troughs is replenished when necessary eitherautomatically or manually. Thus, for example, each of the troughs may be. provided with any well-known liquidlevel control to maintain a body of .developersolution therein. at. a substantially constant level.

The following: examples demonstrate the improvedv results obtained by this invention. In these examples the prints are made byexposing. photographic paper impregnated with. the following compositions:

5 COMPOSITION 1 Percent Chlorostannate of p-diazo diethyl-aniline 2.5 Alum 1.0

Thiourea, 2.0 Ammonium oxalate 2.0

Saponin 0.1

COMPOSITION 2 Percent Nitrate of pa'radiazoethyl-benzylaniline 1.6 Alum 1.0 Ammonium oxalate 2.0

Gelatine 0.1

COMPOSITION 3 7 Percent Zinc chloride double salt of. 3-chloro-4-diethylamino benzene diazonium chloride 3.0 Tartaric acid 2.0-

Boric acid 1.0 Gelatine .02

The developer solutions used have the following formula:

DEVELOPER SOLUTION 'l Percent Potassium tetraborate-SH O 11.0v Potassiumhydroxide 0.60 Phloroglucinol 0.80 Resorcinol 0.55

5 Thiourea 2.50 Sodium saltofisopropyl naphthalene sulfuric acid 0.10

DEVELOPER SOLUTION 2 Percent 2-hydroxy-3*(N-hydroxyethyl)-naphthamide 2.0 Thiourea 2.0 Dextrose 1,0 Borax 2 Sodium-carbonate 3.4

76 odium butyl naphthalene Sultanate-'- 01 DEVELOPER SOLUTION 3 In all of the above compositions and developer solutions, the percentages are on a weight basis; the rest of the compositions and developer solutions is water. In all examples the application of the developer solution was carried out in the type of equipment shown in Figs. 1 to 4, inclusive, of the drawings.

In Table I which follows is given the amount of developer solution in grams per square meter on the prints leaving the wringer rollers for each of five different speeds employing prints made from photographic paper impregnated with composition 1 and developed with developer solution 1. Table II gives similar data for prints made from photographic paper impregnated with composition 2 and developed with developer solution 2. Table III gives similar data for prints made from photographic paper impregnated with composition'3 and developed with developer solution 3.

Table I Example Speed, feet Amount per minute Table II Example Speed, feet Amount per minute Table III Example Speed, feet .Amount per minute For comparative purposes, there is given in Table IV which follows the amount of developer solution applied to prints by a capillary grooved roller machine equipped with doctor rollers to help compensate for speed differences. The machine used in obtaining the datain Table IV was a commercial machine generally considered tobe one of the better commercial developer machines available prior to our invention. The prints were produced from photographic paper (of the same type as used in the above examples) impregnated with composision 1 above and developed with developer solution 1 above.

Table IV Print Amount speed, Applied in feet per grams per minute square meter It will be noted that, while in Examples 1 to 15, in-

elusive, there is little variation in the amount of developer solution on the prints leaving the wringer rollers, irrespective of the speed of the prints, in the case of the prior known capillary grooved roller machine equipped with doctor rollers, the amount of developer solution applied at 25 feet per minute is approximately 50% greater than that applied at 5 feet per minute. The variation with speed is still greater employing prior known capillary grooved rollers not equipped with additional doctor rollers.

It will be further noted that the present invention effectively avoids excessive moistening of the print and provides for uniform and complete solution coverage, and this irrespective of the speed of movement of the prints within practical operating ranges of speed, i.e., from about six inches per minute to seventy feet per minute or even faster. Moreover, this invention results in the uniform application of developer solution to the prints, leaving the wringer rollers, avoiding large excesses with increase in speed of movement of the prints. Hence, this invention reduces the evaporation load, with consequent improvement in the smoothness and other surface characteristics of the print and a saving in heat and reduc-. tion in size of the dryer or evaporator. In the preferred embodiment of Fig. 8, the passage of the prints through the soaking zone 91 after leaving the applicator rollers 83, 84 and before passing through the wringer rollers 86,

1. The method of applying developer solution to photoprints which comprises continuously feeding films of developer solution to the surfaces of a pair of rotating applicator rollers in an amount such that the rollers upon their rotation form a meniscus of developer solution at the bite between said rollers, the meniscus containing an amount of developer solution in excess of that which the photoprints can take up in their passage therethrough, successively passing photoprints through said meniscus and through said applicator rollers, thereafter passing each photoprint through a soaking zone where the developer solution applied thereto soaks into the photoprints and passing each photoprint from said soaking zone through a pair of wringer rollers which effect the removal of the excess of the developer solution from the photoprints leaving thereon uniformly distributed therethroughout a desired controlled amount of developer solution.

2. The method as defined in claim 1 in which the wringer rollers subject the opposite sides of the photoprints in their passage therethrough to a force of from one to six lbs. per lineal foot.

3. Developer apparatus for applying a developer soluassent 11 tion to photoprints, in combination, a pair of troughs containing developer solution, a pair of feed rollers arranged to rotate in said troughs, a pair of applicator rollers in tangential contact with each other and arranged to receive developer solution from said feed rollers, and a pair of wringer rollers spaced from said applicator rollers to provide a soaking zone between the applicator rollers and the wringer rollers.

4. Apparatus as defined in claim3 in which the periphery of one of saidpair of applicator rollers is in tangential contact with the periphery of one of the feed rollers and the periphery of the other applicator roller of said. pair is in tangential contact with the perpihery of the other feed roller, and in which the periphery of one ofthe wringer rollers of said pair of wringer rollers is insubstantially tangential contact with theperiphery of one of said feed rollers.

5-. Developer apparatus for applying developer solution to photoprints, in combination, a pair of applicator rollers arranged to rotate in peripheral contact with each other,

means for continuously applying developer. solution. to

said applicator rollers to form and continuously maintain in the bite between said rollers a pool of developer solution, means to pass the photoprints through said pool, a pair of wringer rollers spaced from said applicator rollers to provide in such space a soaking zone and meansfor rotating said applicator rollers and said wringer rollers to move the photoprints through said pool of developer solution, said applicator rollers, said soaking zone and said wringer rollers, which wringer rollers effect removal of' excess solution so that each photoprint leaving said wringer rollers has the developer solution uniformly applied thereto and has substantially the same amount of developer solution applied thereto per unit area of the photoprint.

6. A developer apparatus for applying developer solution to photoprints, in combination, a pair of troughs for the developer solution, a pair of feed rollers having one roller partially submerged in the solution of one trough and the other roller partially submerged in the solution of the. other trough, a pair of applicator rollers in tangential feeding contact with each other, one of said applicator rollers being in driving engagement with went the feed rollers of said pair and the other applicator roller being in driving engagement with the other feed roller of said pair, a pair ofwringer rollers spaced from said applicator rollers, one of said wringer rollers being in driving en gagement with one of said feed rollers, said applicator rollers being adapted to receive developer solution from. said'f'eed rollers and to form and continuously maintaine meniscus at the bite between said applicator rollers, said meniscus holding anamountof solution in excess. of that capable of being taken up by the photoprints as they pass theretlirough, said wringer rollers being spaced from theapplicator rollers to provide. a time interval in. the travel of thephotoprints between these two setsof rollers-for the developer solution to soak into the photoprints before the photoprints enter the bite between said wringer rollers,

and said wringer rollers being mounted relative. to each other so as to exert pressure on the photoprints-to remove excess of developer solution thereon resulting inphotoprints leaving said wringer rollers. havingthev desired amount of. developer solution thereon uniformly distributed throughout the entire are thereof.

7. The process of applying developer solution to. photo prints which comprises establishing and continuously- 7 1'2. amount of solution each photoprint is capable of taking up during its passage through said pool, passingeach photoprint'aft'er leaving said po'ol through a soaking zone where the developer"solutiorriapplied' to the photoprint so'ak's thereinto; passing each photoprintfromsaid 's'oaking: zone through a second pool of developer solution and immediately thereafterpressing the opposite sides of each photoprint to remove the excess of developer solution and provide each" photoprint with the d'esir'edamount of 10' a meniscus between a pair of rotating rollers, said pool containing an amount of developer solution in excess over that which the photoprints require for the development, passing the photoprints successively through said pool thus" applying the developer solution to both sides of the photoprints in excess over that which the photoprints require for development, then passing the photoprints through a soaking zone where the developer solution applied to thephotoprints soaks thereinto, at the terminal endof said soaking zoneestablishingv and continuously maintaining a second pool of developer solution: formedas ameniscus between a pair of rotating wringing rollers spaced from the first mentioned pair of rollers toprovide said soaking zone and passing the'photoprints from said soaking zone through said second pool of developer solution and through said wringer rollers to remove the excess of developer solution-and provide each photoprint leaving said wringer rollers with the desired amount of developer solution uniformly distributed throughout the entire area thereof.

9. Developer apparatus for applying a developer solution to photoprints, in combination, a pair of troughs for the developer solution, a pair of solution feed rollers arranged to rotate in said troughs, a pair of applicator rollers in tangential contact with each other for feeding said photoprints therebetween and arranged to receive devoloper solution from said feed rollers and to form and continuously maintain a pool of developer solution at the bite between said applicator rollers, a pair of wringer rollers spaced from said applicator rollers to provide in such space a soaking zone for the developer solution to soak into the photoprints after they leave said applicator rollers and before the photoprints enter the bite between said wringer rollers, one-of said wringer rollers being in driving engagement with one of said feed rollers and said wringer rollers effecting removal of excess developer solution so that each photoprint leaving said wringer rollers has substantially the same-amount of developer solution applied thereto per unit area of the photoprint.

References Cited in the file of this patent UNITED STATES PATENTS 248,731 Gardner Oct. 25, 1881 1,867,594 Rowe July 19, 1932 2,241,104 Van der Grinten May 6, 1941 2,562,457 Hannay et al.. July 31, 1951 2,605,684 Nagels et al. Aug. 5, 1952 FOREIGN PATENTS 7,844 France Sept. 3, 1907 137,488 Switzerland Apr. 16, 1 930 853,262 Germany Oct; 23, 1952 744,243 Great Britain ......-.r Feb. 1,- 1956 1,110,571 France' Oct. 12, 1955 758,928 Great Britain Oct. 10, 1956 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Joseph Hruby et a1,

e above numbered patertified that error appears in th atent should read as It is hereby .c

d that the said Letters P ent requiring correction an corrected below.

column 8 line Column 4, line 38, for "of" read on; 18, for "there from" read therefrom line 56, for ".02" read 0,2 column 9 lines 6 and 7, for "l. l5", each oceurrence read 0.15 column 11, line 64, for "are" read area Signed and sealed this 10th day of October 1961o (SEAL) Attest:

W. SWIDER DAVID L LADD Commissioner of Patents Attesting Officer USCOMM-DC UNITED STATES ATENT. OFFICE @CETHEQATE OF GORECTION Patent No 2,981,171 April 25 1961 Joseph Hruby et a1,

It is hereby certified that error appears in the above numbered pa ent requiring correction and that the said Letters Patent. should read as corrected below Column 4, line 38, for "of" read on column 8 line 18 for "there from" read therefrom line 56 for "n02" read 062 column 9 lines 6 and 7, for "115" each occurrence read 0.15 column 11, line 64, for "are" read area Signed and sealed this 10th day of October 1961.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Commissioner of Patents Attesting Officer USCQM M-DC- 

